1. Field of the Invention
This invention relates to improvements in the construction of rocker arms as used in overhead cam shaft internal combustion engines of modern automobiles. In these applications cam actuated rocker arms engage the valve stems of the intake and exhaust valves and effect reciprocating motion of the stems, thus opening and closing the valves in predetermined sequence.
Rocker arms of the general type being described herein are constructed with a cam roller rotatably mounted on a shaft supported by side walls of the rocker arms and in a slot-like, bottomless and topless opening in the rocker arm. Lubrication of the cam roller is effected by oil splashing therein in a haphazard manner. Premature failure of the cam roller and thus the rocker arm can result from the lack of lubrication, causing malfunction of the valving and requiring replacement of the rocker arm assembly.
2. Description of Prior Art
Spencer, U.S. Pat. No. 2,385,309, describes a valve actuating mechanism in an overhead cam environment which comprises a rocker arm, supported on a pivot pin, having a cam roller recess in its upper part in which a cam roller is rotatably seated. The rocker arm is constructed with various passages for forced lubrication of the cam roller and the valve stem, oil being supplied through the pivot pin to and through the various passages, making the rocker arm very expensive to manufacture. The passages can become clogged in the event of contamination of the oil supply, requiring removal and cleaning and perhaps replacement of the rocker arm.
Sampietro, U.S. Pat. No. 3,139,870, shows an operating arrangement for the valves of cylinders of an internal combustion engine. Each cylinder has four valves and each valve is actuated by a rocker arm; there are at least two types of rocker arms used. One type has a cam roller journaled at its end; the other type has a cam roller journaled centrally thereof. Both rollers engage the same cam. The patent is silent as to the lubrication of the cam rollers.